This invention relates to a safety device for a current conduting path in a current using or user device that lies between a terminal connection and a ground connection of the user device.
In user devices with a connection between the terminal connection and the ground connection there exists a danger of melting the connecting line when the wrong polarity is used in connecting the user device to the current supply connections. This danger can indeed be avoided by means of at least one diode. However, such an arrangement is not always practical in the necessary location.
A safety device is therefore desirable for cases where the current supply device has a ground connection and this ground connection is connected with one of the terminal connections. In such a case, when the wrong polarization of the current supply acts on the safety device, lying outside of the useful current path, the safety device interrupts a short-circuit current. The actual load element in the user device is protected by a diode behind the terminal connection that is not connected with the ground connection.
The present invention proceeds from a safety device for use in a user device with two terminal connections and a ground connection, according to which the terminal connection, that during normal polarization conducts the same potential as the ground connection, has a diode, as the safety device, placed behind it in the circuit. The actual load element in the user device lies between the further terminal and the connection point of the diode and the ground connection.
The disadvantage of this arrangement is that, during normal operations, a potential difference occurs between the terminal connection, behind which the diode is located, and the ground connection.